diff --git a/src/vm.c b/src/vm.c
index 598e87229..23ed1f8dc 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -664,7 +664,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     ci->mid = mid;
     ci->proc = MRB_METHOD_PROC_P(m) ? MRB_METHOD_PROC(m) : NULL;
 
-    if (ci->proc == NULL) {
+    if (MRB_METHOD_CFUNC_P(m)) {
       ci->stack[0] = self;
       val = MRB_METHOD_CFUNC(m)(mrb, self);
       cipop(mrb);